1. Technical Field
The present invention relates to a display device, and more particularly, to a source driver for controlling a slew rate of a liquid crystal display (LCD) and a method for controlling the slew rate.
2. Discussion of the Related Art
A liquid crystal display (LCD) is one of the most widely used flat panel displays because of its slim profile and low power consumption, etc. For example, an LCD is commonly found in a variety of electronic devices such as flat screen televisions, notebook computers, cell phones and digital cameras.
There are two main types of LCDs currently used in electronic devices; they are active matrix and passive matrix. Since an active matrix type LCD uses thin film transistors (TFTs) as switching elements for displaying moving pictures, the active matrix LCD is much brighter and sharper than passive matrix displays of the same size and generally has a quicker response time. Thus, active matrix displays are increasingly becoming the choice of laptop computer and flat screen television manufacturers.
The active matrix LCD generally includes a liquid crystal panel, a source driver, and a gate driver. The source driver generates a driving voltage to drive a plurality of data lines, and the gate driver drives a plurality of gate lines.
As the active LCD increases in size, the liquid crystal panel also increases in size. The increase in the size of the liquid crystal panel causes an increase in the number of data lines to be driven, resulting in an increased number of output buffers provided in the source driver.
To uniformly display images on the liquid crystal panel, the output buffers are required to have uniform characteristics. For example, characteristics such as slew rate, gain, phase margin, common mode rejection ratio (CMRR), power supply rejection ratio (PSRR), and an AC characteristic are generally required to be uniform. Among them, the slew rate is an important parameter for determining whether image quality is bad or good. For example, the slew rate of the output drivers must be dispersed within a predetermined distribution or the image quality of an active matrix LCD can be degraded.
Accordingly, a need exists for a source driver in which slew rates of output buffers fall within a predetermined distribution so that degradation in the image quality of the active matrix LCD can be prevented.